MK5 Golf GTI
All Things Mk5 => Mk5 General Area => Topic started by: 08micsta on November 18, 2009, 07:27:43 pm
-
Hey guys
I did search..... :innocent:
But does anyone have the link for the thread where Teutonic_Tamer lectured us about how the ECU adapts and what happens when wrong Octane is used etc etc?
Im looking for it urgently :sad1:
Thanks in advance!
Mike
-
Nevermind!
I found it!
:star: :star: :star: :star: :star: :star: :star:
Thanks though :grin:
-
Why not post the link for future reference? :smiley:
-
what was the issue??
-
Why not post the link for future reference? :smiley:
.... x 2 :happy2:
-
Hey guys
I never found the link but I found the part of the lecture I needed. I remembered I emailed it to my dad a while ago.
Here it is:
Modern ECUs are 'adaptive' (sometimes called 'fuzzy logic') - and this means that as well as providing 'instructions' (for how much fuel to inject, when to inject, what advance on the timing, etc) - they also need to 'learn'. They learn by 'reading' information - the most obvious are things like the MAF, crank and cam position sensors, knock sensors, and the likes (and they also learn throttle pedal actuation, brake pedal actuation, and even steering inputs if ESP is fitted). So once they have learned this stuff, which normally needs at least a couple of engine off/engine on cycles - the ECU can then store a slightly revised 'default' setting.
So if you normally use 99 RON, and drive hard making full use of the '99 RON performance' - the ECU will adapt to provide that level of performance as a default. But then if you stick some 95 RON in the tank - the ECU doesn't get 'told' that you have put 95 RON in - and will continue to try and deliver the 99 RON performance. It will initially try to do this by advancing the ignition timing, but the knock sensor will be constantly instructing to retard the timing - so it then trys the next thing - which is to inject more fuel - creating a richer mixture, which is less prone to knocking. Because the engine continues to 'behave' with an increased fuel delivery rate - the engine will appear to perform the same as if it were still using 99 RON - but the ECU will still know that something now isnt quite correct - but still stores some new 'learnings'. Then you get home, park up, turn off the engine, eat, drink and go to bed. The next time you start the engine, the procedure happens all over again - but this time - has already 'learnt' that it needs less advance, and also 'knows' that it shouldn't have been injecting that much fuel as yesterday - so the performance will progressively drop to suit the 95 juice.
And the same happens in reverse. If your ECU has been used to 95 - by then filling up with 99, you arn't gonna get any increase in performance until the ECU has had a couple of 'cycles' to learn the new settings and adapt accordingly.
As written by TT.
Mike
-
Just to add, it doesnt take long at all for an ECU to adapt, just a few cycles most of the time. A cycle is a complete suck-squeeze-bang-blow on all four cyclinders (1-3-4-2 I think).
One of the biggest achilles heels on modern engines, that ruins all the fun, is the prevenance of data received from the lambda sensors in the exhaust - emissions are everything these days and reign over pretty much everything else.
A friend of mine is calibration engineer and works on mostly Audi stuff. He's explained to me in the past the difference between the map they start with (basically pure power) and the finished article. By the time they have pulled in the all the emissions to pass-able levels, the difference is huge and and a lot of the time is what the likes of Revo undo with a remap. This compromise is sometimes why you get hollowed out torque curves and flat spots on an apparently perfectly healthy engine - In the battle between power, fuel economy and emissions, something has to give and it's usually power. He's got all sorts of stories from Bosch engineers he knows, apparently the Veyron is capable of a hell of a lot more without any serious strain on the engine!
-
Would putting an S3 intake cam into my gti throw up a problem then? Just had one fitted by vw, they said car was fine to pick up, and now just had a call back saying management light has come on!